Objectives: The aim of this study was to compare the cytotoxicity of a single bottle adhesive & an all–in-one adhesive with same manufacturing on human gingival fibroblasts. Methods: Primary human gingival fibroblasts were exposed to different dilutions of Adper Prompt L-Pop and Adper single bond(3MESPE,USA). Cytotoxicity were analysed in uncured mode after 20 seconds, 5 minutes and 24 hours. In cured mode, tested materials were eluted with culture medium for 48h . The cells were then exposed to culture medium containing different diluents of two adhesives for 24 and 48 hours. Cytotoxic effects were evaluated using MTT, cell counting and DNA condensation assays . Data were analyzed by a one-way ANOVA followed by a Tukey post test. Results: In uncured mode Prompt L-Pop was more cytotoxic than Single Bond with 20sec treatment at 10
-2 dilution (P<0.05). By increasing the time to 300sec and 24h, the first cytotoxic dilution moved to 10
-3 and Single Bond was more cytotoxic than Prompt L-Pop .In cured mode Single Bond was more toxic than Prompt L-Pop. apoptosis was present in less than 5% of total death in both cured and uncured adhesives. Conclusions: With circumstances of this invitro study , single bond was more cytotoxic than Prompt L-Pop except in uncured mode at 20sec .by increasing the exposure time, smaller amounts of adhesives could be cytotoxic. cytotoxicity is related to material, dilutions, time of exposure and curing. It would be necessary to identify the toxic ingredients of these materials and replace by more biocompatible components.